Year	Number
1980	3229
1981	3365
1982	3505
1983	3697
1984	4475
1985	4832
1986	4915
1987	5516
1988	5626
1989	6232
1990	5205
1991	5173
1992	5571
1993	5035
1994	5827
1995	6763
1996	6646
1997	7635
1998	7705
1999	8360
2000	9421
2001	9193
2002	10544
2003	11839
2004	13550
2005	15128
2006	15471
2007	16771
2008	16937
2009	14453
2010	16644
2011	17461
2012	18502
2013	20263
2014	19966
2015	22546
2016	25791
2017	28031